I just had one of my guns 'cleaned up' that had this frosting. It was very mild but there. Lapping wouldn't take care of it, so a very light hone with a stone did the job. Less than .001 inch was removed. A hone, as opposed to a reamer, makes a perfectly round hole. Even aggressive lapping can be out of round, I think. Clean your guns and when done cleaning, coat the bore with oil is best prevention IMHO. But, remove the oil before shooting, because of fear of rivelling.

Socialism is almost the worst.